glCopyPixels doesn't work on Ubuntu 10.04

I use glCopyPixels to implement that a image (filled in a window) shift from left to right, but it doesn't work and generate a error number, the error number doesn't match any error number define in the documentation of glCopyPixels.Does anyone know what is the problem?
PS:The Video card I use is ATI Radeon HD 5670 and the driver support GL 4.2